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| Adult Cat Flea |
A common parasite throughout the world, fleas feed on the blood of their victims; the vast majority of which are mammals, though several species are also known to feed on birds. But they started out feeding on reptiles.
Survivors since the Jurassic, ancestral "giant fleas," probably didn't feed on the small mammals of the time, but rather on warm-blooded, feathered dinosaurs. Only later did they begin to find our ancient ancestors appealing and develop a taste for mammal blood.
And they have been a burden for mammals ever since. As many parasites are, fleas are vectors (transmitters) of diseases like tapeworms and most famously, the bubonic plague. In Europe during the 14th century, the plague, or "black death," devastated the continent's population. Estimates range from one-third, to half of all of Europe died at the hands of the the plague bacteria: Yersinia pestis; A parasite transmitted to Europe by fleas riding on rats from Asia.
A wingless insect, the flea gets around and from hosts to host with its impressive jumping ability. Like Superman, before his writers gave him the cheap ability to fly, fleas can jump over 150 times their own body height. For a 6 foot tall male, that would be equivalent to jumping 900 feet high; almost enough to jump over two Great Pyramids of Giza stacked on top of each other.
There are thousands of different species of flea throughout the world, but the most commonly encountered in North America is the cat flea: Ctenocephalides felis. Despite its name, the cat flea common on both cats and dogs. The good news about this species is that they like your pets, Not you. The cat flea cannot subsist on human blood alone, or at least not without some effort. Given enough time on a human host, an adult may be able to produce viable eggs, but this is rare to say the least.
The bad news is that just because they can't survive on you, doesn't seem to stop them from trying. Humans will often get bit when young fleas leap onto them from the person's pet or carpet. Seasoned adults seem to stick to one host for their entire life, so be warned: If you are getting bit, it means they are multiplying.
Flea larva are identifiable as small, white, hairy worms. Though the eggs are laid on the host pet, they are usually shaken off onto the ground or carpet. Then they hatch. The small white larva luckily do not feed on the blood of unsuspecting victims like their parents, but instead on carpeting or fallen organic material. Soon enough the larva wrap themselves into a cocoon, and wait. And wait. And wait.
Once the larva are fully formed, fleas can go for months without feeding. In their cocoons, fleas can sense the vibrations of an approaching victim, or can just the carbon dioxide animals breath out, and they time their emergence accordingly. Inexperienced and hungry, the newly emerged fleas will leap for the first warm-blooded creature they sense. Though they will ultimately decide that your feline or canine companions make for better meals, many people suffer from the initial attack. This leaping from the carpet to the host leads to the ankle-bites that many people experience. If bitten, a flea bite should be fairly identifiable. Red, itchy and swollen, the pattern of bites often comes in groupings of three; the disturbing, but aptly named "breakfast, lunch, and dinner configuration."
Sources:
http://www.nature.com/nature/journal/v483/n7388/full/nature10839.html
http://news.bbc.co.uk/2/hi/health/1576875.stm
http://www.abc.net.au/science/articles/2008/01/29/2149185.htm
http://science.howstuffworks.com/zoology/insects-arachnids/flea.htm
http://www.pestworldforkids.org/fleas.html
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7419.html
http://extension.entm.purdue.edu/publichealth/insects/flea.html
http://www.jstor.org/discover/10.2307/2845085?uid=3739560&uid=2&uid=4&uid=3739256&sid=21101615905371
http://delusion.ucdavis.edu/fleas.html
Photo by Ralph Williams at Purdue University.
Photo Source: http://extension.entm.purdue.edu/publichealth/insects/flea.html
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